Solid electrolyte capacitor and manufacturing method thereof

ABSTRACT

A solid electrolyte capacitor includes a sintered body that is provided by sintering a molded body containing a mixture of metal powder and an inorganic additive. An anode lead wire is disposed to be partially inserted into the sintered body. The sintered body includes an air gap provided where the inorganic additive is removed after sintering of the molded body. A method of manufacturing the solid electrolyte capacitor is also provided.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the priority and benefit of Korean PatentApplication No. 10-2014-0183257, filed on Dec. 18, 2014, with the KoreanIntellectual Property Office, the disclosure of which is incorporatedherein by reference.

BACKGROUND

The present disclosure relates to a solid electrolyte capacitor and amanufacturing method thereof.

Tantalum (Ta) is a metal that is widely used in industries such as theaerospace industry and the defense industry, as well as in themechanical engineering industry, the chemical industry, the medicalindustry, the electrical products industry and the electronics industry,due to having excellent mechanical and physical properties such as ahigh melting point, excellent ductility and corrosion-resistantproperties.

In particular, among a wide variety of metals, tantalum can form arelatively more stable anode oxide film, and thus has been widely usedas an anode material for a small-sized capacitor.

Moreover, recently, the worldwide use of tantalum has sharply increasedby approximately 10% every year due to the rapid development ofinformation technology (IT) industries such as the electronics industryand the information communications industry.

A tantalum capacitor has a structure in which a gap generated when atantalum powder is sintered and coagulated is utilized. Tantalum oxide(Ta₂O₅) may be formed on a surface of tantalum as an electrode metalthrough an anodizing method. The formed tantalum oxide is used as adielectric material, on which a manganese oxide (MnO₂) layer may beformed as an electrolyte.

In addition, due to the lead-out of a cathode, a graphite layer and ametal layer formed of silver (Ag) may be formed on the MnO₂ layer.

Recently, in accordance with the development of small-sized, highcapacitance products, nanoparticles have been used to manufacturetantalum devices, and thus impregnation properties of a porous body havebeen deteriorated. The impregnation property may reflect the amount offluid (such as capacitor oil) that the capacitor can be impregnated withso as to increase the capacity/capacitance of the capacitor.

That is, using tantalum nanoparticles as tantalum powder may secure highspecific surface area to implement high capacitance with a small sizedcapacitor. However, in a case in which tantalum nanoparticles are used,impregnation properties of a manganese nitrate aqueous solution or aconductive polymer solution used as a cathode layer may be deteriorated.

Therefore, it may be difficult to implement high capacitance of aproduct and ensure low equivalent series resistance (ESR)

SUMMARY

An exemplary embodiment in the present disclosure may provide a solidelectrolyte capacitor capable of having high capacitance and excellentequivalent series resistance (ESR) characteristics by containing asintered body having excellent impregnation properties.

According to an exemplary embodiment in the present disclosure, a solidelectrolyte capacitor may include a sintered body and an anode leadwire. The sintered body includes a molded body containing a mixture ofmetal powder and an inorganic additive.

The anode lead wire is disposed to be partially inserted into thesintered body. The sintered body includes an air gap where at least aportion of the inorganic additive is removed.

According to an exemplary embodiment in the present disclosure, a methodof manufacturing a solid electrolyte capacitor may include forming amolded body by stirring metal powder and an inorganic additive andmolding the same. A compressed body is formed by compressing the moldedbody. A sintered body is formed by sintering the compressed body. An airgap is formed by removing the inorganic additive from the sintered bodyafter sintering.

BRIEF DESCRIPTION OF DRAWINGS

The above and other aspects, features and advantages of the presentdisclosure will be more clearly understood from the following detaileddescription taken in conjunction with the accompanying drawings, inwhich:

FIG. 1 is a cross-sectional view of a molded body which is formed aspart of manufacturing a solid electrolyte capacitor according to anexemplary embodiment in the present disclosure;

FIG. 2 is a cross-sectional view of a compressed body which is formed aspart of manufacturing the solid electrolyte capacitor according to theexemplary embodiment in the present disclosure;

FIG. 3 is a cross-sectional view of a sintered body which is formed aspart of manufacturing the solid electrolyte capacitor according to theexemplary embodiment in the present disclosure;

FIG. 4 is a perspective view of a solid electrolyte capacitor accordingto an exemplary embodiment in the present disclosure;

FIG. 5 is a cross-sectional view of the solid electrolyte capacitortaken along line A-A′ of FIG. 4; and

FIG. 6 is a cross-sectional view of a solid electrolyte capacitoraccording to another exemplary embodiment in the present disclosure.

DETAILED DESCRIPTION

Hereinafter, embodiments of the present disclosure will be described indetail with reference to the accompanying drawings.

The disclosure may, however, be embodied in many different forms andshould not be construed as being limited to the embodiments set forthherein. Rather, these embodiments are provided so that this disclosurewill be thorough and complete, and will fully convey the scope of thedisclosure to those skilled in the art.

In the drawings, the shapes and dimensions of elements may beexaggerated for clarity, and the same reference numerals will be usedthroughout to designate the same or like elements.

Solid Electrolyte Capacitor

FIG. 1 is a cross-sectional view of a molded body 110 which is formed inorder to manufacture a solid electrolyte capacitor 100 according to anexemplary embodiment, FIG. 2 is a cross-sectional view of a compressedbody 120 which is formed in order to manufacture the solid electrolytecapacitor 100 according to the exemplary embodiment, and FIG. 3 is across-sectional view of a sintered body 130 which is formed in order tomanufacture the solid electrolyte capacitor 100 according to theexemplary embodiment.

Referring to FIGS. 1 through 3, the solid electrolyte capacitor 100,according to the exemplary embodiment, may include the sintered body 130formed by sintering a molded body containing a mixture of metal powder111 and an inorganic additive 112 and an anode lead wire 113 disposed tobe partially inserted into the sintered body 130, wherein the sinteredbody 130 may include air gaps 114 formed by removing the inorganicadditive 112 after sintering.

The sintered body 130 may be formed by compressing and sintering themolded body 110 containing the metal powder 111 and the inorganicadditive 112.

In detail, the molded body 110 may be formed by stirring the metalpowder 111 and the inorganic additive 112 at a predetermined ratio andmolding the mixture of the metal powder 111 and the inorganic additive112 mixed by the stirring in a rectangular parallelepiped shape, asshown in FIG. 1. Thereafter, after compressing the molded body 110 toform the compressed body 120 of FIG. 2, the sintered body 130 may bemanufactured by sintering the compressed body under high temperature andvibration conditions.

The metal powder 111 is not particularly limited as long as it maybeused in the sintered body 130 of the solid electrolyte capacitor 100.For example, the metal powder 111 may include at least one selected fromthe group consisting of tantalum (Ta), aluminum (Al), niobium (Nb),vanadium (V), titanium (Ti), and zirconium (Zr). Particularly, thesintered body 130 of the solid electrolyte capacitor 100, according tothe exemplary embodiment, may be formed using tantalum (Ta) powder.

The molded body 110 of the solid electrolyte capacitor 100, according tothe exemplary embodiment, may contain the metal powder 111 and theinorganic additive 112 in a predetermined ratio. The inorganic additive112 is not particularly limited as long as it may be selectively removedwith respect to the metal powder 111 by a solvent after the forming ofthe sintered body 130. In some embodiments, the molded body 110 maycontain substantially only the metal powder 111 and the inorganicadditive 112 without any other powders, particles, or additives.

The inorganic additive 112 used in the solid electrolyte capacitor 100,according to the exemplary embodiment, maybe silica powder. It is easyto selectively remove the silica powder with respect to the metal powder111, and the silica powder is not decomposed or evaporated at the timeof compressing and sintering due to high hardness thereof, and thus itmay be easy to adjust porosity. Further, the silica powder is chemicallystable, the stability thereof may be high while being processed, andmixing properties thereof may be excellent when the silica powder isstirred with the metal powder 111, and thus the silica powder and themetal powder 111 may be uniformly stirred.

A particle size of the inorganic additive 112 may be 1 μm to 10 μm. Whenthe particle size of the inorganic additive 112 is less than 1 μm, asize of the air gaps 114 formed in the sintered body 130 may bedecreased, and this improvement of impregnation properties of the solidelectrolyte capacitor 100 manufactured to include the sintered body 130may be insufficient. Further, when the particle size of the inorganicadditive 112 is more than 10 μm, the size of the air gaps 114 may beincreased, and thus it may be difficult to secure capacitance of thesolid electrolyte capacitor 100.

In other words, a volume of the inorganic additive 112 present in thecompressed body 120 formed by compressing the molded body 110 maycorrespond to a volume of the air gaps 114 in the sintered body 130formed by sintering the compressed body 120. Therefore, in order toimprove the impregnation properties of the solid electrolyte capacitor100 manufactured using the sintered body 130 and secure sufficientcapacitance, the particle size of the inorganic additive 112 may beselected to be within the range of 1 μm to 10 μm.

The sintered body 130 included in the solid electrolyte capacitor 100,according to the exemplary embodiment, may include the air gaps 114. Asdescribed above, the air gaps 114 may exist in the sintered body 130 andbe formed by removing the inorganic additive 112 existing in thesintered body 130. Therefore, a shape of the air gaps 114 may correspondto a shape of the inorganic additive 112 removed from the sintered body130. An example of the air gaps 114 is illustrated in FIG. 3, but theshape of the air gaps 114 is not limited to a spherical shape. That is,the shape of the air gaps 114 may vary. For example, the air gaps mayhave a furrow shape, a groove shape, a depression shape, an indentationshape, or the like.

In general, using tantalum nanoparticles as tantalum powder in a solidelectrolyte capacitor provides a high specific surface area and highcapacitance while having a small size. However, when tantalumnanoparticles are used, impregnation properties of a manganese nitrateaqueous solution or a conductive polymer solution used as a cathodelayer may be deteriorated. Therefore, it may be difficult to obtain aproduct having high capacitance and low equivalent series resistance(ESR).

Since the solid electrolyte capacitor 100, according to the exemplaryembodiment, includes the sintered body 130 having air gaps 114 formed byremoving the inorganic additive 112, impregnation properties may beimproved, and high capacitance and excellent equivalent seriesresistance (ESR) characteristics may nonetheless be implemented.

The solid electrolyte capacitor 100, according to the exemplaryembodiment, may additionally include the anode lead wire 113 disposed tobe partially inserted into the sintered body 130.

The anode lead wire 113 may contain a tantalum ingredient and bepartially inserted into the sintered body 130 of the solid electrolytecapacitor 200 to thereby be connected to external power via an anodelead frame 210 (see FIG. 6), thereby forming an anode.

As illustrated in FIG. 3, the anode lead wire 113 may be disposed insuch a manner that it is led from or extends from one surface of thesintered body 130 of the solid electrolyte capacitor 100. Alternatively,the anode lead wire 113 may be led from or extend from a central portionof the sintered body 130 or may be disposed to be offset from thecentral portion of the sintered body 130.

FIG. 4 is a perspective view of a solid electrolyte capacitor, accordingto an exemplary embodiment, and FIG. 5 is a cross-sectional view of thesolid electrolyte capacitor taken along line A-A′ of FIG. 4.

Referring to FIGS. 4 and 5, the solid electrolyte capacitor 100,according to the exemplary embodiment, may include a dielectric oxidefilm layer 140, a solid electrolyte layer 150, and cathode reinforcementlayers 160 and 170 composed of a carbon layer 160 and a cathode layer170 sequentially layered on an outer surface of the sintered body 130.

The dielectric oxide film layer 140 may be formed by growing tantalumoxide (Ta₂O₅), which is an oxide film, on the outer surface of thesintered body 130 by a formation method using an electrochemicalreaction.

The solid electrolyte layer 150 may be formed on a surface of thedielectric oxide film layer 140. The solid electrolyte layer 150 maycontain at least one of a conductive polymer and manganese dioxide(MnO₂).

In a case in which the solid electrolyte layer 150 is formed of theconductive polymer, the solid electrolyte layer 150 may be formed on thesurface of the dielectric oxide film layer 140 by a chemicalpolymerization method or electro-polymerization method. For a conductivepolymer material, a polymer material having conductivity may be usedwithout any particular limitation. For example, the conductive polymermaterial may contain polypyrrole, polythiophene, polyaniline, or thelike.

Ina case in which the solid electrolyte layer 150 is formed of manganesedioxide (MnO₂), conductive manganese dioxide may be formed on thesurface of the dielectric oxide film layer 140 by dipping the sinteredbody 130, on the surface of which the dielectric oxide film layer 140 isformed, in a manganese aqueous solution such as a manganese nitrateaqueous solution, and pyrolyzing the manganese aqueous solution.

The cathode reinforcement layers 160 and 170 may be formed on the solidelectrolyte layer 150. The cathode reinforcement layers 160 and 170 mayinclude the carbon layer 160 and the cathode layer 170. The carbon layer160 may be formed of a carbon paste. That is, the carbon layer 160 maybe formed by applying the carbon paste onto the solid electrolyte layer150, wherein the carbon paste is dispersed in water or an organicsolvent in a state in which conductive carbon powder such as naturalgraphite or carbon black is mixed with a binder, a dispersant, or thelike.

The cathode layer 170 containing a conductive metal may be disposed onthe carbon layer 160 in order to improve electric connectivity with acathode lead frame 220 (see FIG. 6), wherein the conductive metalcontained in the cathode layer 170 maybe silver (Ag).

FIG. 6 is a cross-sectional view of a solid electrolyte capacitor 200,according to another exemplary embodiment.

Referring to FIG. 6, the solid electrolyte capacitor 200, according toanother exemplary embodiment, may further include an anode lead frame210 connected to an anode lead wire 113 and a cathode lead frame 220connected to cathode reinforcement layers 160 and 170 formed on an outersurface of the sintered body 130. Further, the solid electrolytecapacitor 200 may further include a molding part 230 enclosing thesintered body 130, the anode lead wire 113, the anode lead frame 210,and the cathode lead frame 220. In this case, portions of the anode leadframe 210 and the cathode lead frame 220 may be exposed to the outsideof the molding part 230.

The anode lead frame 210 and the cathode lead frame 220 may be connectedto external power (not illustrated) to allow current to pass through theanode lead wire 113 and the cathode reinforcement layers 160 and 170.That is, the anode lead frame 210 and the cathode lead frame 220 may beexposed to the outside of the molding part 230 to serve as connectionterminals for electric connections with another electronic product.

The molding part 230 may serve to protect the solid electrolytecapacitor 200 from external factors and be mainly formed of an epoxy ora silica based epoxy molding compound (EMC). However, the molding part230 is not limited thereto.

Method of Manufacturing Solid Electrolyte Capacitor

Hereinafter, a manufacturing method of the solid electrolyte capacitor100, according to the exemplary embodiment, will be described withreference to the accompanying drawings. However, in order to avoid anoverlapping description, a description of the same content as describedabove will be omitted.

Referring to FIGS. 1 through 3, the manufacturing method of the solidelectrolyte capacitor 100, according to the exemplary embodiment, mayinclude forming a molded body 110 by stirring and molding metal powder111 and an inorganic additive 112; forming a sintered body 130 bysintering the molded body 110; and forming air gaps 114 by removing theinorganic additive 112 from the sintered body 130. The manufacturingmethod may further include, after the forming of the molded body 110,forming a compressed body 120 by compressing the molded body 110.Thereafter, the sintered body 130 may be formed by sintering thecompressed body 120.

Referring to FIG. 1, mixed powder may be formed by stirring and mixingthe metal powder 111 and the inorganic additive 112 as described aboveusing a stirrer, and the molded body 110 may be formed by molding themixed powder into a suitable shape. Generally, the molded body 110 isformed in a rectangular parallelepiped shape, but the shape of themolded body 110 is not limited thereto. Then, the anode lead wire 113may be inserted into one surface of the molded body. Next, referring toFIG. 2, the compressed body 120 may be formed by compressing the moldedbody 110.

Thereafter, referring to FIG. 3, the sintered body 130 may be formed bysintering the compressed body 120 under high temperature and vibrationconditions. Then, in order to remove the inorganic additive 112contained in the sintered body 130, the sintered body 130 may besubjected to chemical treatment. The chemical treatment may be performedby dipping the sintered body 130 in a solution capable of dissolving theinorganic additive 112. In this case, it may be preferable to select asolution that may dissolve only the inorganic additive 112 but does nothave an influence on other materials included in or configuring thesintered body 130.

When the inorganic additive 112 contained in the sintered body 130 issilica powder, the solution used to dissolve the inorganic additive 112may contain ammonium fluoride. Ammonium fluoride, a silica dissolvingagent, may selectively remove the silica powder from the sintered body130.

The air gaps 114 may be formed in the sintered body 130 by removing theinorganic additive 112 in the sintered body 130 as described above.

Next, referring to FIG. 5, after removing the inorganic additive 112from the sintered body 130, the dielectric oxide film layer 140, a solidelectrolyte layer 150 having a negative polarity, and the cathodereinforcement layers 160 and 170 may be sequentially formed on a surfaceof the sintered body 130.

The dielectric oxide film layer 140 may be formed by growing tantalumoxide (Ta₂O₅), which is an oxide film, on the outer surface of thesintered body 130 by a formation method using an electrochemicalreaction.

Next, the solid electrolyte layer 150 may be formed on a surface of thedielectric oxide film layer 140. The solid electrolyte layer 150 maycontain at least one of a conductive polymer and manganese dioxide(MnO₂).

In a case in which the solid electrolyte layer 150 is formed of aconductive polymer, the solid electrolyte layer 150 may be formed on thesurface of the dielectric oxide film layer 140 by a chemicalpolymerization method or electro-polymerization method. For theconductive polymer material, a polymer material having conductivity maybe used without any particular limitation. For example, the conductivepolymer material may contain polypyrrole, polythiophene, polyaniline, orthe like.

Ina case in which the solid electrolyte layer 150 is formed of manganesedioxide (MnO₂), conductive manganese dioxide may be formed on thesurface of the dielectric oxide film layer 140 by dipping the sinteredbody 130 (on the surface of which the dielectric oxide film layer 140 isformed) in a manganese aqueous solution such as a manganese nitrateaqueous solution, and pyrolyzing the manganese aqueous solution.

Next, the cathode reinforcement layers 160 and 170 may be formed on thesolid electrolyte layer 150. The cathode reinforcement layers 160 and170 may include a carbon layer 160 and a cathode layer 170. The carbonlayer 160 may be formed of a carbon paste. That is, the carbon layer 160may be formed by applying the carbon paste onto the solid electrolytelayer 150, wherein the carbon paste is dispersed in water or an organicsolvent in a state in which conductive carbon powder such as naturalgraphite or carbon black is mixed with a binder, a dispersant, or thelike.

The cathode layer 170 containing a conductive metal may be disposed onthe carbon layer 160 in order to improve electric connectivity with acathode lead frame 220 (see FIG. 6), wherein the conductive metalcontained in the cathode layer 170 maybe silver (Ag).

FIG. 6 illustrates the solid electrolyte capacitor 200 further includingan anode lead frame 210, a cathode lead frame 220, and a molding part230.

Referring to FIG. 6, the solid electrolyte capacitor 100 includes thesintered body onto which the above-mentioned cathode layer 170 isapplied, and the anode lead wire 113. Additionally, the anode lead frame210 may be formed to contact the anode lead wire 113, and the cathodelead frame 220 may be formed to contact the cathode reinforcement layers160 and 170 formed on the outer surface of the sintered body 130. Theanode lead frame 210 and the cathode lead frame 220 may be formed of aconductive metal such as a nickel/iron alloy, or the like.

The anode lead frame 210 and the cathode lead frame 220 may be disposedin parallel with each other, while being spaced apart from each other. Alower surface of each of the anode lead frame 210 and the cathode leadframe 220 maybe exposed to a lower surface of the molding part 230, andthus the anode lead frame 210 and the cathode lead frame 220 may be usedas connection terminals for electric connection with another electronicproduct.

The anode lead frame 210 may be formed to contact the anode lead wire113. Contact portions between the anode lead frame 210 and the anodelead wire 113 may be bonded by electric welding or using a conductiveadhesive.

The cathode lead frame 220 may be formed to be flat in order to increasebonding strength with the cathode reinforcement layers 160 and 170, andthus an area of a bonded portion between the cathode lead frame 220 andthe cathode reinforcement layers 160 and 170 may be increased. Anadhesive layer (not illustrated) may be formed on an upper surface ofthe cathode lead frame 220 using a conductive adhesive, or the like, andthe cathode reinforcement layers 160 and 170 may be mounted thereon sothat one surface thereof contacts the adhesive layer. The conductiveadhesive may contain an epoxy based thermosetting resin and a conductivematerial, wherein the conductive material may contain at least one ofsilver (Ag), gold (Au), palladium (Pd), nickel (Ni), and copper (Cu).

Next, the molding part 230 may be formed to enclose the sintered body130 on which the cathode reinforcement layers 160 and 170, the anodelead wire 113, the anode lead frame 210, and the cathode lead frame 220are applied/mounted. The molding part 230 may be formed by transfermolding a resin such as an epoxy molding compound (EMC). In this case,the molding part 230 may be formed to partially expose the anode leadframe 210 and the cathode lead frame 220.

As set forth above, according to exemplary embodiments, the solidelectrolyte capacitor having improved impregnation properties may beobtained, and thus high capacitance and excellent equivalent seriesresistance (ESR) characteristics may be implemented.

While exemplary embodiments have been shown and described above, it willbe apparent to those skilled in the art that modifications andvariations could be made without departing from the scope of the presentinvention as defined by the appended claims.

What is claimed is:
 1. A solid electrolyte capacitor comprising: asintered body including a molded body containing a mixture of metalpowder and an inorganic additive; and an anode lead wire disposed to bepartially inserted into the sintered body, wherein the sintered bodyincludes an air gap where at least a portion of the inorganic additiveis removed.
 2. The solid electrolyte capacitor of claim 1, wherein theinorganic additive is silica powder.
 3. The solid electrolyte capacitorof claim 1, wherein the inorganic additive has a particle size of 1 μmto 10 μm.
 4. The solid electrolyte capacitor of claim 1, wherein a shapeof the air gap corresponds to a shape of the inorganic additive removedfrom the sintered body.
 5. The solid electrolyte capacitor of claim 1,wherein the metal powder includes at least one selected from the groupconsisting of tantalum (Ta), aluminum (Al), niobium (Nb), vanadium (V),titanium (Ti), and zirconium (Zr).
 6. The solid electrolyte capacitor ofclaim 1, further comprising: a dielectric oxide film layer, a solidelectrolyte layer having a negative polarity, and a cathodereinforcement layer which are sequentially layered on a surface of thesintered body.
 7. The solid electrolyte capacitor of claim 6, whereinthe solid electrolyte layer is formed of at least one selected from thegroup consisting of manganese dioxide (MnO₂) and a conductive polymer.8. The solid electrolyte capacitor of claim 6, wherein the cathodereinforcement layer is provided by sequentially applying carbon andsilver (Ag).
 9. The solid electrolyte capacitor of claim 1, wherein thesintered body includes an air gap where all of the inorganic additive isremoved.
 10. A method of manufacturing a solid electrolyte capacitor,the method comprising: forming a molded body by stirring metal powderand an inorganic additive and molding the same; forming a sintered bodyby sintering the molded body; and forming an air gap by removing theinorganic additive from the sintered body after sintering.
 11. Themethod of claim 10, wherein the inorganic additive is silica powder. 12.The method of claim 10, wherein the inorganic additive has a particlesize of 1 μm to 10 μm.
 13. The method of claim 10, wherein the inorganicadditive is removed by dipping the sintered body in a solutioncontaining ammonium fluoride.
 14. The method of claim 10, wherein themetal powder includes at least one selected from the group consisting oftantalum (Ta), aluminum (Al), niobium (Nb), vanadium (V), titanium (Ti),and zirconium (Zr).
 15. The method of claim 10, wherein after removingthe inorganic additive from the sintered body, a dielectric oxide filmlayer, a solid electrolyte layer having a negative polarity, and acathode reinforcement layer are sequentially formed on a surface of thesintered body.
 16. The method of claim 15, wherein the solid electrolytelayer is formed of at least one selected from the group consisting ofmanganese dioxide (MnO₂) and a conductive polymer.
 17. The method ofclaim 15, wherein the cathode reinforcement layer is formed bysequentially applying carbon and silver (Ag).